1. Field of the Invention
This invention relates generally to the medical surgical field and, in particular, to the field of laser surgery.
2. Related Art
Surgical applications of lasers are well known in modern medicine. The types of lasers are nearly as numerous as the procedures that use them, and selection of a laser for any given procedure depends upon the laser-tissue interaction, which phenomena have been widely reported, and the desired outcome of that interaction. The types of lasers may be grouped into ultraviolet (193-351 nm), visible wavelength (400-700 nm), and infrared (700-100,000 nm) lasers.
Of the infrared lasers, the carbon dioxide (“CO2”) laser (with a wavelength of approximately 10.6 microns) is utilized most widely for surgical applications of ablation and cutting of tissue because the laser energy from a CO2 laser can cut, cauterize and ablate human and animal tissue. Additionally, CO2 lasers are also more readily available and more economical because they cost much less than other types of surgical lasers.
Moreover, the energy of a CO2 laser is readily absorbed by water, which is the primary component of most biological tissue. This results in minimal thermal spread and makes CO2 lasers very useful for applications near critical anatomical structures. As an example, a CO2 laser's absorption in water is almost 400 times greater than that of an Argon laser.
Since approximately 60-70% of tissue is water, high absorption of CO2 laser's energy in water implies that there will also be high absorption in tissue. This results in a superficial effect in which a CO2 laser's energy is limited in its spread within a given target of tissue. Thus, a CO2 laser has a superficial action limited to the upper layers of tissue when compared with other energy sources, and minimal damage to adjoining tissue volume. In addition, a CO2 laser's energy seals small blood vessels as it cuts through the tissue rendering it an enhanced scalpel that combines precise cutting, ablation and microvascular coagulation while incurring minimal collateral thermal damage.
Unfortunately, while efficient optical waveguides (also known as fiber waveguides, fiber-optic waveguides, optical fibers, fibers, or lightpipes) exist for transmitting low amounts of energy particularly in the visible region, it is difficult to create an efficient waveguide, particularly a flexible waveguide, for transmitting relatively high amounts of energy, particularly in the infrared region, because of the lack of materials capable of efficiently transmitting power in this region. Specifically, a CO2 laser cannot be delivered through quartz fiber optics, or silica or sapphire lenses, since these materials are opaque at the 10.6 micron wavelength. Materials that are commonly utilized with CO2 laser light, both as lenses and as mirrors, include sodium chloride, potassium chloride, zinc selenide (“ZnSe”), and germanium. In early CO2 laser designs, the CO2 laser light was typically directed through a series of mirrors in a complex articulating system through which the light is delivered to a handpiece containing a lens which would allow the beam to be focused in a non-contact manner onto a target location.
As such, early CO2 laser system included at least one CO2 laser, an associated power supply, optical components (such as mirrors and lenses), and control electronics that occupy substantial space and floor area. This situation limited the application of CO2 lasers somewhat in surgical applications. Also, it is necessary to carry the laser light energy from the laser system into the surgical field—i.e., the place in the operating room where the patient, nurses and surgeon maintain a sterile environment. Sterility of laser surgical implements must be maintained so as to avoid nosocomial or other types of infections that could prove hazardous to the patient and his recovery from the surgical procedure.
As an example, these early CO2 laser surgical systems included articulated optical arms with diagonal mirrors placed at rotating joints that were use to carry laser light energy through the arm to a surgical hand piece which included optics that focused the laser light energy so that the energy could be directed at tissue in the sterile surgical field. These articulated arms proved to be unergonomic and awkward to use, limited to “line-of-sight” surgical procedures, and they were too large for many surgical procedures performed in, for example, body cavities in the nose, bronchia, ears, or throat. As a result these systems fell into relative disuse because of these difficulties.
In order to overcome many of these problems, companies such as, for example, OmniGuide Inc. of Cambridge, Mass., developed novel small hollow core, thin, and flexible optical waveguides capable of delivering CO2 laser energy through fibers mounted in handpieces attached to a variety of tips. Before utilizing this novel optical waveguide approach (such as, for example, BeamPath™ fibers produced by OmniGuide Inc.), conventional optical waveguides were used to guide laser light through solid core fibers via a process known as index guiding or total internal reflection. This form of transmission is dependent on the transparency of the material through which the light propagates, and thus carries with it all the limitations of the constituent material. As an example, the most acute limitation is that of light transmission across different wavelengths because, for example, silica's transmission window ranges from 300 nm to 2,000 nm, which is opaque to far infrared wavelengths.
Examples of these novel small hollow core, thin, and flexible optical waveguides include, for example, the BeamPath™ fibers produced by OmniGuide Inc., which are photonic bandgap fibers with each fiber having forty or more microscopic layers of alternating glass and polymer that form a reflective system known as a Bragg diffraction grating. The wavelength of light transmitted by this structure is a function of the thickness of the glass/polymer bi-layers, and may be varied.
These novel small hollow core, thin, and flexible optical waveguides are generally described by: U.S. Pat. No. 7,349,589, titled “Photonic Crystal Fibers and Medical Systems including Photonic Crystal Fibers,” issued, Mar. 25, 2008, to Temelkuran et al.; U.S. Pat. No. 7,331,954, titled “Photonic Crystal Fibers and Medical Systems including Photonic Crystal Fibers,” issued, Feb. 19, 2008, to Temelkuran et al.; U.S. Pat. No. 7,349,589, titled “Photonic Crystal Waveguides and Systems Using Such Waveguides,” issued, Dec. 18, 2007, to Fink et al.; U.S. Pat. No. 7,231,122, titled “Photonic Crystal Waveguides and Systems Using Such Waveguides,” issued, Jun. 12, 2007, to Weisberg et al.; U.S. Pat. No. 7,190,875, titled “Fiber Waveguide Formed From Chalcogenide Glass and Polymer,” issued, Mar. 13, 2007, to Anderson et al.; U.S. Pat. No. 7,167,622, titled “Photonic Crystal Fibers and Medical Systems including Photonic Crystal Fibers,” issued, Jan. 23, 2007, to Temelkuran et al.; U.S. Pat. No. 7,142,756, titled “High Index-Contrast Fiber Waveguides and Applications,” issued, Nov. 28, 2006, to Anderson et al.; U.S. Pat. No. 7,072,553, titled “Low-Loss Photonic Crystal Waveguide Having Large Core Radius,” issued, Jul. 4, 2006, to Johnson et al.; U.S. Pat. No. 6,903,873, titled “High Omnidirectional Reflector,” issued, Jun. 7, 2005, to Joannopoulos et al.; U.S. Pat. No. 6,898,359, titled “High Index-Contrast Fiber Waveguides and Applications,” issued, May 24, 2005, to Soljacic et al.; U.S. Pat. No. 6,895,154, titled “Photonic Crystal Optical Waveguides having tailored dispersion profiles,” issued, May 17, 2005, to Johnson et al.; U.S. Pat. No. 6,879,386, titled “Optical Waveguide Monitoring,” issued, Apr. 12, 2005, to Shurgalin et al.; U.S. Pat. No. 6,879,386, titled “Optical Waveguide Monitoring,” issued, Nov. 9, 2004, to Shurgalin et al.; U.S. Pat. No. 6,801,698, titled “High Index-Contrast Fiber Waveguides and Applications,” issued, Oct. 5, 2004, to King et al.; U.S. Pat. No. 6,788,864, titled “High Index-Contrast Fiber Waveguides and Applications,” issued, Sep. 7, 2004, to Ahmad et al.; U.S. Pat. No. 6,728,439, titled “Electromagnetic Mode Conversion In Photonic Crystal Multimode Waveguides,” issued, Apr. 27, 2004, to Weisberg et al.; U.S. Pat. No. 6,625,364, titled “Low-loss Photonic Crystal Waveguide Having Large Core Radius,” issued, Sep. 23, 2003, to Johnson et al.; and U.S. Pat. No. 6,563,981, titled “Electromagnetic Mode Conversion In Photonic Crystal Multimode Waveguides,” issued, May 13, 2003, to Weisberg et al., all of which are herein incorporated by reference in their entirety.
Unfortunately, while these novel small hollow core, thin, and flexible optical waveguides have advantages over the other known approaches in the prior art, this approach still suffers from several problems. As an example, in FIG. 1, a system diagram of an example of a known implementation of a small hollow core optical waveguide 100 is shown. The small hollow core optical waveguide 100 may include an outer tubular shell 102 having a distal end 104 and hollow core 106, where the hollow core (also known as a central lumen) 106 and outer tubular shell 102 define an outer lip 108 at the distal end 104. In an example of operation, the small hollow core optical waveguide 100 receives CO2 laser energy at an input (not shown) to the small hollow core optical waveguide 100 and, in response, produces an output laser beam 110 that exits the distal end 104 in an axial direction 112 with a fan shaped energy distribution. In FIG. 1, the output laser beam 110 is shown having an initial radius 114 at the distal end 104 and then three stop sizes 116, 118, and 120 that increase in radius 122, 124, and 126, respectively, as the distance 128, 130, and 132, respectively, from the distal end 104 is increased. The output laser beam 110 has a fan shaped energy distribution because the small hollow core optical waveguide 100 is not a mode preserving device—i.e., it does not preserve the Gaussian energy distribution of a TEM00 laser beam.
This presents several practical problems to a surgeon attempting to use this small hollow core optical waveguide 100 for surgery because precise surgery in small body cavities, on small structures of tissue, depends upon precisely positioning the laser beam 110 and moving it over the tissue in an accurate fashion so as to cut or ablate tissue. With the small hollow core optical waveguide 100, shown in FIG. 1, this is very difficult because the sharpest part of the laser beam 110 is closest to the distal end 104 of the small hollow core optical waveguide 100. This means that the surgeon must attempt to keep the laser beam 110 at a close and uniform distance from the tissue (not shown). This distance is very difficult to control with a hand-held probe being used in small confined body cavities. When a surgeon cuts using the prior art waveguide 100 he, or she, is in danger of varying the cut width causing areas of cauterization, and ablation creating a jagged rough edge that may have areas of charred or carbonized tissue. This occurs because as the distance from the tissue to the laser beam 110 varies, the energy delivered to the tissue varies and can diverge to the point of charring tissue instead of ablating tissue.
As a practical matter, the prior art waveguides (such as the small hollow core optical waveguide 100) need to be cooled by blowing air or gas through the central lumen of the waveguide during surgery because the dielectric coating in the waveguide is “lossy” and it is not an efficient reflector of CO2 laser light energy which causes the waveguide to heat up. In a typical surgery, the waveguide is often bent, and if too severely bent, may result in the laser beam burning through the sidewall of the waveguide causing catastrophic failure, stopping the surgery until the waveguide is replaced, lengthening the patient's exposure to anesthesia, and creating general inconvenience for the surgical staff.
Another disadvantage of the waveguide 100 design is that a diverging laser beam 110 would require intermediate optical lenses if the waveguide 100 is to be joined or extended. Lenses are not desirable for CO2 laser light, because of their transmission losses and they are generally composed of toxic materials such as ZnSe.
Because the fiber must be continuous, without junctions or breaks in the waveguide from the laser to the surgical handpiece, the surgical probe designs are limited to hollow tubes that require insertion of the waveguide in order to create a usable surgical instrument.
As such, there is a need for a CO2 laser surgical system that solves the above mentioned problems.